1. Field of the Invention
The present invention relates to networks. More specifically, the invention provides a system for determining alternate routes in a network using a connection-oriented protocol.
2. Background
Networks provide a mechanism for exchanging data between various nodes in the network and between devices coupled to the network. Various types of protocols may be used for propagating data through a single network or through multiple interconnected networks. A connection-oriented protocol is an example of a network routing protocol which establishes a connection between a source and a destination and transfers data along the established connection. The established connection typically includes a series of links through intermediate nodes in the network. Once the connection has been established, all data for a particular data flow travels across the same path. Asynchronous Transfer Mode (ATM), Internet Stream Protocol, Ver. 2 (ST2) and Frame Relay are examples of connection-oriented protocols.
Connection-oriented protocols may include Quality of Service (QoS) requirements for transferring or routing data through a network. QoS may be specified in terms of minimum bandwidth requirements, transmission delay, the amount of memory or buffer space required for the data flow, and other resource parameters. In systems using QoS parameters, various links in the network may be incapable of providing adequate resources for the required QoS. In these situations, it is necessary to locate a path through the network in which each node and link along the path has adequate resources to support the requested data flow. Thus, if the normal routing procedures identify a path containing one or more links without adequate resources for the requested data flow, an alternate path must be identified. If an alternate path having adequate resources cannot be identified, then a connection refusal signal is generated and propagated back to the source indicating that the requested QoS is not available to the destination.
Various procedures may be used for identifying an alternate path through the network between a source and a destination. One approach for identifying an alternate path considers every possible path through the network. Although this approach provides the greatest likelihood that an acceptable alternate path will be located, the approach is time-consuming and requires considerable computational resources each time an alternate path must be identified. Therefore, it is desirable to provide a system for identifying alternate paths requiring less time and computational resources than the approach discussed above.